1. Field of the Invention
The present invention relates to IC sockets, test methods using the same and IC socket mounting mechanisms, and more particularly, to an IC socket for testing a semiconductor device (IC) having projection electrodes formed as bumps or the like, a test method using such an IC socket and a mechanism for mounting such an IC socket.
Many of the ICs used recently are constructed to have projection electrodes formed as solder bumps for connection with an external device, for the purpose of reducing the size of a package. For example, a ball grid array (BGA) has such a construction. Demands for high-density, high-speed semiconductor devices having projection electrodes are growing for further reduction in the package size. Associated with this, pitch between electrodes is on a decreasing trend; and projection electrodes are being arranged with an increasingly higher density and on an increasingly reduced scale.
Once produced, the ICs are subject to a performance test to see if a prescribed performance is provided. The ICs are tested by being mounted on an IC socket. Therefore, the IC socket should be adapted for the high-density, small-scale trend of the ICs. As a result of the high-density, small-scale trend, the strength of each projection electrode has become extremely low so that it is necessary to ensure that the projection electrodes are not damaged when brought into contact with contact pins provided in the IC socket.
2. Description of the Related Art
FIGS. 1-5 show a construction of a conventional IC socket 1. As shown in FIGS. 1-3, the IC socket 1 generally comprises a socket body 2, a lid 3, contact pins 4 and a substrate 5. The IC socket 1 is designed so that an IC 7 of a BGA type provided with solder bumps 6 (projection electrodes) is mounted on the IC socket 1 and tested for its performance.
The socket body 2 includes a cavity 8 in which the substrate 5 is fitted. The cavity 8 is provided with through holes 9 aligned with the solder bumps 6 formed in the IC 7. The substrate 5 is provided with mounting holes 10 also aligned with the solder bumps 6 formed in the IC 7.
The contact pins 4 are formed by punching a thin metal plate so as to have a crooked configuration that provides a spring action as shown in FIGS. 2 and 3. The contact pins 4 have contact parts 4a, formed at the upper end thereof, inserted into mounting holes 10 of the substrate 5. Terminal parts 4b formed at the lower end the contact pins 4 are inserted into the through holes 9 formed in the cavity 8 and are made to project from the bottom of the socket body 2. The same number of the crooked contact pins 4 is provided as the number of solder bumps 6 formed in the IC 7. The contact pins 4 are designed to remain press-fitted into the through holes 9 and the mounting holes 10 while being accommodated in the IC socket 1.
The lid 3 is rotatably fitted to the socket body 2 by a pivot part 11. By closing the lid 3 when the IC 7 has been mounted on the socket body 2, the lid 3 presses the IC 7 toward the substrate 5. As a result, the bumps 6 formed in the IC 7 are pressed against the contact parts 4a of the contact pins 4. The contact pins 4 are elastically deformed so as to press the solder bumps 6 by the elastic action. Accordingly, the contact pins 4 and the solder bumps 6 are electrically connected. A lock lever 12 is provided in a lid 3. The lock lever 12 locks the lid 3 in the closed position.
The IC socket 1 having the above-described construction is designed to be mounted on a test board 13 by a solder reflow process or the like after the terminal parts 4b projecting from the underside of the socket body 2 are inserted into through holes 14 formed in the test board 13. The test board 13 is connected to a test device (for example, a burn-in test device) for performing a test of the IC 7. Thus, a prescribed test is performed on the IC 7 mounted on the IC socket 1 via the test board 13.
It is known that a thin oxide film 15 (see FIG. 5) is formed on the surface of the solder bumps 6 formed in the IC 7. Since the oxide film 15 has a low conductivity, it is necessary to penetrate the oxide film 15 in order to establish an electrical connection between the solder bumps 6 and the contact pins 4.
Conventionally, as shown in FIG. 4 showing the part A indicated by the arrow in FIG. 3 on an enlarged scale, the elastic deformation of the contact pins 4 occurring when the lid 3 is closed is utilized. More specifically, it is expected that the elastic deformation causes the contact parts 4a of the contact pins 4 to be displaced in the direction indicated by the arrow of FIG. 4 so that the contact parts 4a slide on the surface of the solder bumps 6 such that the contact parts 4a penetrate the oxide film 15.
With the increasingly smaller solder bumps 6 provided on the IC 7 recently, the strength of the solder bumps 6 has decreased. Accordingly, the method whereby the contact parts 4a are expected to penetrate the oxide film 15 by sliding on the surface of the solder bumps 6 produces a deformation in the solder bump 6 while the contact parts 4a slide on the surface thereof. The deformation of the solder bumps is indicated by the arrow 6a of FIG. 5. If any of the solder bumps 6 is deformed, a variation in the height of the solder bumps 6 occurs when the IC 7 is mounted on a circuit board or the like after the test. The solder bumps 6 may not be properly mounted on the circuit board.
In the conventional IC socket 1, a high level of precision is required to provide the contact pins 4 having a crooked configuration that provides a spring action in the socket body 2. The press-fitting of the crooked contact pins 4 demands intensive attention. Another problems is that, as the size of the contact pins 4 become smaller with the reduction in the size of the solder bumps 6, it is increasingly difficult to produce the contact pins 4 having a complex crooked configuration, and the cost of the production increases accordingly.
Accordingly, it is an object of the present invention to provide an IC socket, a test method using the same and an IC socket mounting mechanism.
Another and more specific object of the present invention is to provide an IC socket, capable of performing high-precision testing without damaging small projection electrodes, a test method using such an IC socket and an IC socket mounting mechanism for mounting such an IC socket.
In order to attain the aforementioned. objects, the present invention provides an IC socket mounted on a test board while in use and having a semiconductor device with projection electrodes mounted on said IC socket for testing, said IC socket is constructed such that a diameter of a plurality of straight contact pins having a first end electrically connected to said test board and a second end thereof connected to said projection electrodes is sufficiently small for each of said plurality of contact pins to pierce said projection electrodes, said IC socket being electrically connected to said test board by said first end of said plurality of contact pins piercing said projection electrodes.
According to the IC socket of the present invention described above, one end of each of the contact pins constituting the contact unit is electrically connected to a test board and the other end is connected to the projection electrodes. Thus, an electrical connection is properly established between the projection electrodes and the test board.
By configuring the diameter of the contact pin to be small enough for the contact pin to pierce the projection electrode for an electrical connection therewith, it is ensured that, even if an insulating film such as an oxide film is created on the projection electrode, the contact pin can be electrically connected to the projection electrode by penetrating the insulating film.
Since the contact pin has a significantly small diameter, the projection electrode is not deformed, only a fine hole being created in the projection electrode when pierced by the contact pin. Thus, a high-precision mounting of an IC is possible.
Even with its fine diameter, it is highly unlikely that the contact pin is bent or curved because the contact pins are supported by the supporting structure constituting the contact unit. Therefore, an electrical connection is properly established between the contact pin and the projection electrode.
The aforementioned objects may also be attained by an IC socket mounted on a test board while in use and having a semiconductor device with projection electrodes mounted on said IC socket for testing, said IC socket comprising: a plurality of straight contact pins having a first end electrically connected to said test board and a second end connected to said projection electrodes; and a supporting structure for supporting said plurality of contact pins, each of said plurality of contact pins provided at the second end with a deformable part deformable according to a pressure occurring between said contact pin and an associated one of said projection electrodes.
According to the IC socket according to the present invention described above, deformation of the deformable part provided at that portion of the contact pin which is connected with the projection electrode cancels a variation in the height of the projection electrodes or a variation in the pressure caused by an irregularity on the surface of the test board. Since the deformable part is deformed in conformity to the configuration of the projection electrodes, a relatively large contact area is secured. Thus, the deformable part is suitable for improving an electrical conductivity between the contact pins and the projection electrodes.
Even when the projection electrodes are formed of a soft metal such as a solder, the pressure applied to the projection electrodes is relatively small as a result of the deformable part being deformed. Accordingly, an electrical connection can be properly established between the contact pins and the projection electrodes without causing damage in the projection electrodes.
The aforementioned objects may also be attained by an IC socket mounting mechanism for mounting, on a test board, an IC socket comprising a contact unit having a plurality of straight contact pins for electrically connecting the test board and projection electrodes of a semiconductor device and also having a supporting structure for supporting said plurality of contact pins, the test board included in said IC socket mounting mechanism being provided with through holes to which said plurality of contact pins are electrically connected, and each of said plurality of contact pins having one end thereof connected to said test board and provided with an elastically deformable part so that an elastic resilient force generated when said elastically deformable part is inserted in an associated one of said through holes causes said contact pin to be pressed against the through hole and to establish an electrical connection therewith.
According to the IC socket mounting mechanism of the present invention, a relatively simple operation of inserting the elastically deformable part into the through hole ensures that an electrical connection is established between the contact pins and the test board. Since the elastically deformable part in the through hole presses the through hole by an elastic resilient force, an improved electrical connection between the contact pins and the test board is established.
The present invention also provides an IC socket mounting mechanism for mounting, on a test board, an IC socket comprising a contact unit having a plurality of straight contact pins for electrically connecting the test board and projection electrodes of a semiconductor device and also having a supporting structure for supporting the plurality of contact pins, the test board included in the IC socket mounting mechanism being provided with through holes at a pitch greater than a pitch at which the projection electrodes are arranged, and each of the plurality of contact pins is configured to be long enough to extend from the supporting structure to reach an associated one of the through holes formed in the test board.
According to the IC socket mounting mechanism described above, the through holes can be arrayed at a relatively wide pitch even if the pitch at which the projection electrodes are arrayed is relatively small. Thus, forming of the through holes becomes easier, and forming of the wiring pattern provided on the test board for connection with the through holes also becomes easier.
The aforementioned may also be attained by an IC test system for testing a semiconductor device mounted on an IC socket which is mounted on a test board connected to a test device, the IC socket being constructed such that a diameter of a plurality of straight pins having a first end electrically connected to the test board and a second end thereof connected to the projection electrodes is sufficiently small for each of the plurality of contact pins to pierce the projection electrodes, the IC socket being electrically connected to the test board by the first end of the plurality of contact pins piercing the projection electrodes.
The present invention further provides an IC test system for testing a semiconductor device mounted on an IC socket which is mounted on a test board connected to a test device, said IC socket comprising: a plurality of straight contact pins having a first end electrically connected to said test board and another end connected to said projection electrodes; and a supporting structure for supporting said plurality of contact pins, each of said plurality of contact pins provided at the second end with a deformable part deformable according to a pressure occurring between said contact pin and an associated one of said projection electrodes.
According to the IC test system of the present invention, the reliability of the test on a semiconductor device can be improved because an electrical connection between the projection electrodes of the semiconductor device and the contact pins of the IC socket can be properly established.